1. Field of the Invention
The present invention relates generally to video signal processors for a printer and, more particularly is directed to a color video still image processing system in which printing color separation data is formed from a color video still image.
2. Description of the Related Art
As is conventional, a color printing original plate is made by using a predetermined one field or one frame of a video signal (i.e., still image signal) generated from a video camera or an electronic still camera. In this case, the video signal from the video camera or from the electronic still camera is converted into digital data of three primary colors R (red), G (green) and B (blue). The digital data R, G and B are converted into reflection density (i.e.,--log conversion), thereby being produced as color separation data of four colors of three primary colors (cyan C, magenta M, yellow Y) of subtractive process and black K. Data of black K is determined by the minimum values of cyan C, magenta M and yellow Y.
Then, original plates of four colors of cyan C, magenta M, yellow Y and black K are made by using respective color data of color separation data of four colors and one color still image is printed by using the original plates of four colors. The color still image is printed by using the color separation data of four colors in exactly the same way such that a color image taken by a halide film is printed.
The color image printed via the original plates made by the video signal is unsatisfactory as compared with the color image printed via the original plate made by the halide film. That is, the video still image has poor hue and color saturation as compared with those of the color still image of the halide film so that the video still image has poor color reproducibility. As a consequence, the color video still image becomes unsatisfactory as compared of the color still image of the halide film. To be more concrete, the color saturation of the color video still image is about 60% of that of the halide film still image so that the color image is hardly printed by using the original plate made by the video signal in the prior art. If the user insists that the color video still image is printed by using the original plate made from the video signal, those who are engaged in making the original plate must adjust hue and color saturation with reference to four color separation data. That is, this color adjustment is a manual labor dependent on the visual sense of those skilled in the art.